During formation of a semiconductor device, various layers (e.g. oxides) require planarization to remove steps or undulations prior to formation of subsequent layers. Planarization is typically performed mechanically by forcing a semiconductor substrate face down against a semi-porous polishing pad which is saturated with an abrasive compound (i.e., a slurry) and by rotating the polishing pad relative to the semiconductor substrate. The slurry reacts with the substrate's surface, which makes the surface easier to remove, and the rotary motion between the polishing pad and the substrate mechanically removes layers of the intermediate oxide and is continued until the oxide steps or undulations are removed.
After polishing, slurry residue is conventionally cleaned or scrubbed from the substrate surfaces via mechanical scrubbing devices, which may employ polyvinyl acetate (PVA) brushes, or brushes made from other porous or sponge-like material, or brushes made with nylon bristles, etc. It is known to combine a scrubbing device with one or more nozzles that output sonically energized fluid. Although such devices may remove the majority of slurry and other particulates from a substrate's surfaces, often residual slurry and other particulates may remain particularly along a substrate's beveled edge, where scrubber brushes and sonic fluid sprays may not uniformly contact the substrate's surface.
Accordingly, a need remains for an improved method and apparatus for simultaneous scrubbing and sonically cleaning a substrate.